We investigated the effects of tumor necrosis factor-alpha (TNF alpha), a cytokine produced as one aspect of inflammatory reactions, on the intracellular free calcium concentration in single pituitary cells using a calcium-sensitive fluorescent dye, indo-1, and a digital imaging fluorescence microscopic system. TNF alpha induced an increase in intracellular free calcium immediately after administration, reaching a peak after 30 sec and then returning to nearly the basal level after 120 sec in the pituitary cells. The cells responding to TNF alpha constitute about 15% of the pituitary cell population, and these cells never responded to the hypothalamic releasing hormones TRH, GnRH, GH-releasing hormone, or CRH. To define the role of calcium in TNF alpha-induced PRL release, dispersed pituitary cells were exposed to agents that modify TNF alpha-induced calcium mobilization. Such calcium channel blockers as cobalt and verapamil decreased basal and TNF alpha-induced PRL release. A low calcium medium also decreased TNF alpha-induced PRL release. These data suggest that intracellular calcium mobilization may be involved in the process of TNF alpha-induced PRL release.
Abstract. The present study was designed to characterize bihormonal cells in rat pituitary cells which secrete PRL and gonadotropins.This was done by using sandwich cell immunoblot assay (CIBA) and reverse hemolytic plaque assay (RHPA) in combination with immunocytochemistry (ICC) and by measuring the intracellular free calcium concentration ([Ca2+];). The result of the experiment with sandwich CIBA revealed that the populations of LH-and FSH-secreting cells in the PRL-secreting cells were 6.23% and 5.91%, respectively, and the populations of the PRL secreting cells in the LH-and FSHsecreting cells were 18.4% and 15.5%, respectively. Additional studies by the combined techniques of RHPA with ICC revealed that the populations of LH-and FSH-containing cells in the PRL secreting cells were 4.43% and 2.40%, respectively, which were consistent with the results of Sandwich CIBA. Some of the PRL-secreting cells determined by RHPA showed responsiveness to TRH and GnRH in [Ca2+];. These results suggest that bihormonal cells which secrete both PRL and LH, or both PRL and FSH are present in the normal rat pituitaries.
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